Re: Where is the missing disk space gone?

[Tyler MacDonald <tyler@yi.org>]

Michael Yang <michael.yxf@gmail.com> wrote:
> physically missing. I used "df -h", it returns to me with the follows:
> /dev/sda8              19G  334M   18G   2% /home
>
> When I used "du -sh /home", it returns to me with the actual used spaces:
> 162M    /home

  I'm not 100% sure on this... but I have noticed the same thing on my
system... I think it may be extra space used for the filesystem journal. Eg;
my /boot partition is only using 19 megs, but it claims to be using 23. 

  Okay, so I'm curious too, so I'm going to test it now.

  I remove my journal from /boot (umount it, then tune2fs -O ^has_journal
/dev/hda1), and I get:

# df -h /boot
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda1              38M   19M   18M  53% /boot

  Then re-add the journal (tune2fs -j /dev/hda1) and I get:

# df -h /boot
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda1              38M   23M   14M  64% /boot

  I suggest keeping the journal around. :-)

  One other thing to note: all ext2/ext3 filesystems are created with 5% of
the free disk space reserved for root. That is, once there is only 5% of the
disk space free, the partition will show as "100%" used and only root can
continue writing to it. This makes sense for "/", "/var", etc... it might
not make so much sense for /home. You can get an immediate 5% free space
gain by running:

  tune2fs -m0 /dev/hdwhatever

  Hope this helps,
    Tyler